The present invention relates generally to a filtering column having a filtering media containing a special bottom and multiple branched pipes as collectors.
Filtering reaction columns are well known for use in processes for separation of components in a feed solution, for example for use in ion exchange resin reactions and as reactors for immobilized enzymes. These columns generally have large diameters in order to maximize column capacity, but as diameter increases it is difficult to maintain uniform flow through a column cross-section.
Uniform flow is critical for efficient use of these columns. Recently, in order to produce better uniform flow, the use of flat bottoms has been recommended in ion exchange resin columns. The use of columns with a flat bottom has also been proposed for continuous chromatographic separation processes similar to those processes disclosed in U.S. Pat. No. 4,267,054. In the latter case, several filtering columns may be used, connected by a pipe line, and the liquid must flow uniformly through the cross-section of each column, without back mixing and without dead space between columns.
In the past, filtering columns have had filtering media constructed with a layer of silicic sand, or a large number of strainers, on a perforated plate. Liquid is filtered through these media, collected on a spherical panel, and flows out from the center of the panel. This type of structure is undesirable because the flow tends to "short cut," i.e., to be greater, at the center of the column than at the periphery, and also dead spaces exist at the spherical panel which cause undesirable back mixing.
In an attempt to reduce these problems, filtering columns have been manufactured with a plurality of branched pipes distributed uniformly on the flat bottom of the column, the pipes having small holes on their undersides and being covered by a filtering screen. These branched pipes connect to gathering pipes, which take fluids to an outlet. However, this structure can still result in back mixing and non-uniform flow, as illustrated in FIG. 1.
FIG. 1, which is labeled "PRIOR ART," is a side sectional view of a part of the flat bottom of the column previously described, illustrating two branched pipes 1 on the flat bottom 4. The branched pipes 1 have small holes 3 at their undersides, and are covered by a filtering screen 2. The course of the liquid flow is illustrated by the arrows.
It is clear that the course of the flow down to the point between the two branched pipes 1 is longer than the course of flow straight to the branched pipes 1. Since these two courses do not have the same distance, the liquid flow into the branched pipe 1 is mixed with two kinds of flow, which are former and later inleted liquids. In other words, the fluid entering pipes 1, from the two different flow paths, is a mixture of fluid from two different heights in the column. This is known as back mixing. Also, the point 5 at the center of the two branched pipes 1 is a dead spot in the flow. This known structure thus does not collect liquid maintaining a uniform flow through the filtering column.